Octacalcium phosphate (OCP) is a metastable phase of calcium phosphate preferentially crystallized from a solution thereof under a pH condition of 4 to 7, and is a precursor of an apatite. From the research so far, it has been known that this OCP is useful as a bone regeneration material, an organic molecule adsorbing material, and a catalyst supporting material (see Non Patent Literatures 1 to 3). Further, it is expected that, by imparting a porous structure to this material, bone regeneration reaction, organic molecule adsorption reaction and catalytic effect, all of which are reactions occurring via the surface of the material, are promoted.
OCP is not sinterable, and it is impossible to produce a shaped product with a complicated shape utilizing a curing process of the shaped product over the course of sintering. The known methods such as the drop method by LeGeros and the method using a three-way pipe by Suzuki et al. can produce OCP powder or granule, but the maximum size of OCP that can be formed is not more than 1.0 mm3 (see Patent Literature 1, and Non Patent Literatures 4 and 5).
This conventional OCP shaped product is produced via crystal growing process, and therefore, the granule size is the largest size it can be. When it is used as a bone regeneration material, it is necessary to embed a large number of granules to the bone defect part (see Non Patent Literature 6). Further, the size and shape of voids between granules formed at this moment is not necessarily the optimal shape for the application. Furthermore, there is also a risk that granules flow out due to factors such as blood flow and air flow.
In order to solve such problems, there is a need to make the size of the shaped product 2.0 mm3 or more.